In this report, local electronic structures of steps and terraces on rutile TiO(2) single crystal faces were studied by second harmonic and sum frequency generation (SHG∕SFG) spectroscopy. We attained selective measurement of the local electronic states of the step bunches formed on the vicinal (17 18 1) and (15 13 0) surfaces using a recently developed step-selective probing technique. The electronic structures of the flat (110)-(1×1) (the terrace face of the vicinal surfaces) and (011)-(2×1) surfaces were also discussed. The SHG∕SFG spectra showed that step structures are mainly responsible for the formation of trap states, since significant resonances from the trap states were observed only from the vicinal surfaces. We detected deep hole trap (DHT) states and shallow electron trap (SET) states selectively from the step bunches on the vicinal surfaces. Detailed analysis of the SHG∕SFG spectra showed that the DHT and SET states are more likely to be induced at the top edges of the step bunches than on their hillsides. Unlike the SET states, the DHT states were observed only at the step bunches parallel to [1 1 1] [equivalent to the step bunches formed on the (17 18 1) surface]. Photocatalytic activity for each TiO(2) sample was also measured through methylene blue photodegradation reactions and was found to follow the sequence: (110) < (17 18 1) < (15 13 0) < (011), indicating that steps along [0 0 1] are more reactive than steps along [1 1 1]. This result implies that the presence of the DHT states observed from the step bunches parallel to [1 1 1] did not effectively contribute to the methylene blue photodegradation reactions.

Recent studies have shown that IGZO are variously influenced by photoirradiation. In this study, by using measurement results of optical properties and calculation results, a relationship of defect levels in the IGZO films and the SiO 2 films to negative-bias photodegradation was examined, and the mechanism of the degradation was revealed.

1 Introduction A metamaterial is an artificial composite with an exotic electromagnetic response that is not readily found in nature. It consists of a unit with a size smaller than the wavelength of the incident electromagnetic wave while much larger than the atomic scale. Such a composite can be regarded as an effective new material, the properties of which can be designed artificially by its structure.In 1967, Veselago considered wave propagation in a material with negative permittivity and negative permeability (double negative material) [1]. He noticed that light can propagate in such a medium but in a strange way: The wave vector and the Poynting vector are opposite in sign. It is referred to as a left-handed material because electric, magnetic and wave vectors form a left-handed triad. At the interface between an ordinary material and such an extraordinary medium, the light refracts in a "wrong" direction in order to conserve the tangential component of wave vectors and energy flow at the interface. Thus the refractive index of this material is understood to be negative in this case.In 1999, Pendry pointed out that it is possible to realize negative permeability by use of artificial composites [2]. In 2000, Smith demonstrated that the double negative material at microwave regime with the use of split-ring resonators (SRR) and a metal wire array [3].So far in metamaterial research, SRRs and their derivatives have been mainly used in order to modify permeability. The magnetic-field component of the incident light induces an electric current inside the ring, and then the induced magnetic field negates the incident magnetic field, which changes the magnetic permeability. The cut in the ring works as a capacitor that accumulates charge carried by the current. The inductance of the ring and the capacitance determines the resonance frequency of SRR.It can be shown that the material with nonunity permeability exhibits an optical response that does not occur in ordinary materials. For instance, in ordinary transparent materials such as quartz, the reflectivity for p-polarization vanishes at a certain incident angle (Brewster's angle). But as can be seen from the Fresnel equations below, Brewster's angle of s-polarization can also exist, if permeability is not unity:We demonstrate that the optical reflectivity for s-polarized light vanishes at a certain angle in a stratified metal -dielectric metamaterial numerically and experimentally. The metamaterial consists of a unit cell where a Ag layer of 30 nm thickness is sandwiched by Al 2 O 3 layers of 60 nm thickness. In order to understand the phenomenon in terms of effective permittivity and permeability, we extended a field-sampling method. The permeability is found to be significantly different from unity, which is the origin of Brewster's angle for s-polarization. The microscopic field distribution is readily coarse grained with the effective optical parameters. The present result is a manifestation of the magnetic response in the optical regime. where r s , r p ar...

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